In U.S. Pat. No. 2,103,185 Rumpler, issued Dec. 21, 1937, it is proposed to form a hollow engine crankshaft with progressively increasing wall thickness toward the output end in order to accommodate the accumulative gas forces transmitted by the journals, crankpins and crankarms as the output end is approached.
While such a crankshaft design may be appropriate for some engine configurations, the patent's teachings apparently fail to consider that a crankshaft has finite stiffness and will have resonant frequencies excited by the firing loads and/or the engine speed. The absence of concern for torsional vibration in Rumpler's patent is a reflection of the typically lower maximum speed of engines in 1937. The loads caused by torsional vibration of todays high speed engines, commonly operating in the neighborhood of 7-8,000 RPM, must be accounted for in the design in addition to the gas forces.